At IACR International Cryptology Conference, CRYPTO 2018 in Santa Barbara Paul Rösler presented the paper "Towards Bidirectional Ratcheted Key Exchange". In this work Bertram Poettering and Paul Rösler defined and constructed one of the core primitives of instant messaging: the key update mechanism named "ratcheting". In contrast to "ratcheting" protocols deployed in major messenger like Signal, the protocols designed in the presented paper provably reach security in a comprehensibly strong attacker model. For full details see the extended version of the paper: https://eprint.iacr.org/2018/296.pdf

The paper "More is Less: On the End-to-End Security of Group Chats in Signal, WhatsApp, and Threema" by Paul Rösler, Christian Mainka, and Jörg Schwenk will be presented at IEEE EuroS&P 2018 next week in London.